Poor video editing detection system

ABSTRACT

A system for detecting poor video editing detects a television (TV) image signal. When a TV image originates from a film signal rather than a video signal, a de-interlacing device performs a de-interlacing at a film signal mode to thereby increase a vertical resolution of a TV image signal. A sawtooth detector can detect a poor video editing, which causes a sawtooth occurrence to TV image signals, on an unbroadcasted TV image signal. Accordingly, the poor video editing is found in advance. Also, the invention uses a scene change in combination with the sawtooth detector to thereby avoid a poor edited image and obtain a preferred image quality.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a detecting system and, moreparticularly, to a system for detecting poor video editing.

2. Description of Related Art

For the limited broadcast bandwidth, current TV broadcasting typicallyuses alternate odd/even fields. As shown in FIG. 1, odd fields 10 and 12have only odd-line video data, and even fields 11 and 13 have onlyeven-line video data. New generation of TVs requires a higher verticalresolution, and accordingly a line doubler is used in a TV to perform adouble frequency processing in order to increase the verticalresolution. The simplest double frequency processing is to directlymerge adjacent odd and even fields to thereby form a progressive scanframe. However, because of a time difference between the adjacent oddand even fields, such a processing presents a sawtooth to a motionimage.

To overcome the aforementioned problem, a line doubler preferably isequipped with a frame motion detector to detect a motion image. Inaddition, the line doubler can perform an inter-field interpolation ofde-interlacing process on a still image and an intra-field interpolationof de-interlacing process on the motion image.

Another double frequency processing is achieved by determining if animage originates from a film. It is known that a film is formed byrecording 24 frames per second. Accordingly, for displaying a filmsignal on an NTSC TV, it converts the 24 frames into 60 fields persecond. As shown in FIG. 2, such a conversion is typically referred toas a “3:2 pull down”, i.e., two temporally successive film frames areconverted into three fields and two fields respectively. For example,frame 14 is converted into field 18 (odd field), field 19 (even field)and field 20 (odd field), frame 15 is converted into field 21 (evenfield) and field 22 (odd field), and so on. Thus, upon such a doublefrequency processing, a perfect double frequency output can be obtainedby combining all odd and even fields that correspond to the same framewhen an image is determined to originate from a film signal. In thiscase, an image has no sawtooth and a motion image can have the highestvertical resolution.

For detecting an image source, frame or field motion data is used todetermine whether the image source is a film signal or not. FIG. 3 showsan example of using frame motion detectors 31 to provide the requiredframe motion data. As shown in FIG. 3, each frame motion detector 31 candetect two successive odd or even fields to thereby output ‘1’ when thetwo successive odd or even fields are the same and ‘0’ when different.Accordingly, if a TV image is a segment of still frames, whether theimage source is a film signal or not, the frame motion detector 31outputs a sequence ‘11111, 11111, . . . ’. If the TV image is a segmentof motion video signal, the frame motion detector 31 outputs a sequence‘00000, 00000, . . . ’. If the TV image is a segment of motion filmsignal, the frame motion detector 31 outputs a sequence ‘10000, 10000, .. . ’.

The output of the frame motion detector 31 is applied to FIG. 4 in whicha film detection state transition diagram is shown, thereby determiningif an input image is of a 3:2 pull down film. States 0-5 of the filmdetection state transition diagram are video mode states, and states6-10 are film mode states. As shown in FIG. 4, the diagram starts atstate 0. For every input with ‘10000’, the state transition has to passthrough state 4, which causes an increase on the counter 41. When thecounter 41 exceeds a threshold, a state transition from state 4 to state6 is performed, i.e., a TV image (video) mode state is changed into afilm mode state.

As cited above, when an input image is of the 3:2 pull down film, theframe motion detector outputs ‘10000’ or ‘1111’. When the frame motiondetector outputs a certain amount of ‘10000’, the film detection statetransition diagram is changed from a video mode state to a film modestate and remains at the film mode state as long as the input is metwith ‘1XXXX’.

The aforementioned technique can effectively detect whether an imageoriginates from a film signal or not, and have a perfect doublefrequency output. However, it also causes the poor film editing, whichimpairs the 3:2 pull down proportion and outputs the image with asawtooth. As shown in FIG. 5, fields 1-8 are from a film segment A, andfields 9-16 are from another film segment B. Due to a bad editing in thefilm segment B, field 9 and the following fields are not consistent withthe 3:2 pull down process. Please refer again to FIG. 4 and the statetransition diagram can only determine that the image is fit to the filmmode at field 11. Therefore, when the field 9 is used as a basis togenerate the television image, the field 9 and the field 10 originallyfrom different film frames are combined into one image frame, and thetelevision image incurs sawtooth effect as a result.

To overcome the aforementioned problem, U.S. Pat. No. 6,201,577 grantedto Peter D. Swartz for a “Film source video detection” discloses amethod for detecting a poor editing. The method detects the poor editingon a current output image and informs a film pattern detector to leavethe film mode to thereby avoid combining two fields, which are not of asame frame, into a frame. However, such a detection is operated on thecurrent output image, which cannot totally avoid an image frompresenting a sawtooth because a line doubler outputs a frame with asawtooth before a poor editing is detected. In addition, the prior artcannot leave the film mode in states 7-10 and thus possibly combines twofields of different frames into a frame, resulting in likely presentinga sawtooth to a TV image.

Therefore, it is desirable to provide an improved system for detectingpoor video editing to mitigate and/or obviate the aforementionedproblems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a system for detectingpoor video editing, which can reduce the use amount of frame buffers andline buffers to thereby reduce the hardware cost.

Another object of the present invention is to provide a system fordetecting poor video editing, which can detect and process various poorediting to thereby obtain a preferred image quality.

In accordance with one aspect of the present invention, there isprovided a system for detecting poor video editing. The system receivesplural fields of a video datastream for detecting a poor editing in thevideo datastream. The system includes a film mode detector, a sawtoothdetector and a scene detector. The film mode detector receives aprevious field F[N−1] and a next field F[N+1] respectively of the videodatastream to accordingly determine whether the video datastream is of afilm mode or not. The sawtooth detector receives a current field F[N]and the next field F[N+1] respectively of the video datastream tothereby determine whether a sawtooth is present to the next field F[N+1]based on a field energy of the current field F[N] and a frame energy ofthe current field F[N] and next field F[N+1]. The scene detectorreceives the current field F[N], the next field F[N−1] and the previousfield F[N−1] in order to calculate a field brightness difference betweenthe current field F[N] and the previous and next fields F[N−1] andF[N+1], and accordingly determines whether a scene change occurs. Whenthe video datastream is of the film mode and the scene change occurs,the video datastream is determined to have the poor editing, for thepoor editing mostly occurs at the scene change.

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing display fields of a video signal;

FIG. 2 is a schematic view of typical fields converted from a filmsignal;

FIG. 3 is a schematic view of typically using a frame motion detector toprovide the required frame motion data;

FIG. 4 is a film detection state transition diagram;

FIG. 5 is a schematic view showing a typical poor edited film signal;

FIG. 6 is a block diagram of a system for detecting poor video editingin accordance with the invention;

FIG. 7 is a block diagram of a sawtooth detector in accordance with theinvention;

FIG. 8 is a schematic view of using a scene detector to calculate afield brightness difference of a current field in accordance with theinvention; and

FIG. 9 is a state transition diagram of a system operation in accordancewith the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 6 is a block diagram of a system for detecting poor video editingin accordance with the invention. As shown in FIG. 6, the systemreceives plural fields F[Z] of a video datastream for detecting a poorediting in the video datastream, wherein Z=N indicates a current fieldin processing. The system includes a film mode detector 610, a sawtoothdetector 620, a scene detector 630, a de-interlacing device 640, adirect coupler 650, a determinator 660 and a multiplexer 670.

The de-interlacing device 640 receives a current field F[N], a previousfield F[N−1] and a next field F[N+1] respectively of the videodatastream and accordingly uses a de-interlacing to produce the framefor the current field F[N].

The direct coupler 650 receives the previous field F[N−1], the currentfield F[n] and the next field F[N+1] respectively of the videodatastream to accordingly produce the frame for the current field [N]directly.

The film mode detector 610 receives the previous field F[N−1] and thenext field F[N+1] respectively of the video datastream to accordinglydetermine whether the video datastream is of a film mode or not. Whenthe video datastream is not of a film mode, the film mode detector 610outputs states 0 to 5, and when the video datastream is of a film mode,the film mode detector 610 sequentially outputs states 6 to 10, i.e.,film mode 6 to 10, which can be implemented by those skilled in theprior art in accordance with the state transition diagram of FIG. 4 andthus a detailed description is deemed unnecessary.

The sawtooth detector 620 receives the current field F[N] and the nextfield F[N+1] respectively of the video datastream to thereby determinewhether a sawtooth is present to the next field F[N+1] in accordancewith a field energy of the current field F[N] and a frame energy of thecurrent field F[N] and next field F[N+1]. When the frame energy isgreater than the number of pixels of the field energy of the currentfield F[N] and exceeds a threshold, the sawtooth detector determinesthat the sawtooth is present to the next field F[N+1].

The field energy of a pixel can be expressed by:|Luma_(F[N])[i][j]−Luma_(F[N])[i+1][j]|,   (1)where Luma_(F[N])[i][j] indicates a brightness of pixel (i, j) of thecurrent field F[N] and Luma_(F[N])[i+1][j] indicates a brightness ofpixel (i+1, j) of the current field F[N]. The frame energy of a pixelcan be expressed by:|Luma_(F[N])[i][j]−Luma_(F[N+1])[i][j]|,   (2)where Luma_(F[N])[i][j] indicates a brightness of pixel (i, j) of thecurrent field F[N] and Luma_(F[N+1])[i][j] indicates a brightness ofpixel (i, j) of the next field F[N+1].

FIG. 7 is a block diagram of the sawtooth detector 620 in accordancewith the invention. In FIG. 7, the sawtooth detector 620 includes a linebuffer 621, subtractors 622 and 623, absolute devices 624 and 625,comparators 626 and 627 and a counter 628. For a sawtooth detection, thesawtooth detector 620 first uses a reset signal to reset the counter628. The subtractor 623 subtracts the current field F[N] (with the pixelbrightness Luma_(F[N])[i][j]) from the next field F[N+1] (with the pixelbrightness Luma_(F[N+1])[i][j]) and a brightness difference between thefields F[N] and F[N+1] is obtained. Because one of the fields F[N] andF[N+1] is an odd field and the other is an even field, the distancebetween the fields F[N] and F[N+1] is one pixel in vertical. Inaddition, the brightness difference between the fields F[N] and F[N+1]is referred to as a frame energy of the current field F[N].

The line buffer 621 buffers a line of the current field F[N].Accordingly, the pixel (i, j) of the current field F[N] is passedthrough the line buffer 621 to obtain a pixel (i+1, j), which is of aline buffered field F[N]′, and the fields F[N]′ and F[N] are subtractedby the subtractor 622 to thereby obtain a brightness difference betweenthe fields F[N]′ and F[N]. Because the pixel (i+1, j) is obtained byline buffering the pixel (i, j), the distance between the pixels (i+1,j) and (i, j) is two pixels in vertical. The brightness differencebetween the fields F[N]′ and F[N] is referred to as a field verticalenergy of the current field F[N].

The frame energy and field energy of the current field F[N] are passedthrough the absolute devices 624 and 625 to obtain the absolute valuesrespectively for further comparison by the comparator 626. Since thedistance between the fields F[N] and F[N+1] is smaller than the distancebetween the fields F[N]′ and F[N], i.e., one pixel is smaller than twopixels, the frame energy is smaller than the field energy. If thecomparator 626 finds the frame energy greater than the field energy, itmay indicate an occurrence of sawtooth and the counter 628 is increasedby one. When the counter 628 exceeds a threshold, a sawtooth presentsignal is output to inform the film mode detector 610 of leaving thefilm mode.

In this embodiment, the sawtooth detector 620 receives the current fieldF[N] and the next field F[N+1] respectively of the video datastream tothereby determine whether a sawtooth is present to the next field F[N+1]in accordance with the field energy of the current field F[N] and theframe energy of the current field F[N] and next field F[N+1]. In otherembodiments, the sawtooth detector 620 can receive the current fieldF[N] and the previous field F[N−1] respectively of the video datastreamto thereby determine whether a sawtooth is present to the current fieldF[N] in accordance with the field energy of the previous field F[N−1]and the frame energy of the previous field F[N−1] and current fieldF[N].

The scene detector 630 receives the current field F[N], the next fieldF[N+1] and the previous field F[N−1] in order to calculate a fieldrightness difference Diff_Luma between the current field F[N] and theprevious and next fields F[N−1] and F[N+1], and accordingly determineswhether a scene change occurs.

FIG. 8 is a schematic view of using the scene detector 630 to calculatethe field brightness difference Diff_Luma of the current field F[N] inaccordance with the invention. The scene detector 630 depends on thefollowing equation to calculate the field brightness differenceDiff_Luma of the current field F[N]:Diff_Luma=max(|Y _(F[N−1]) −Y _(F[N]) |, |Y _(F[N+1]) −Y _(F[N])|),  (3)where Y_(F[N−1)] indicates a brightness average of the previous fieldF[N−1], Y_(F[N]) indicates a brightness average of the current fieldF[N] and Y_(F[N+1]) indicates a brightness average of the next fieldF[N+1]. The brightness average of the current field F[N] is expressedby:

$\begin{matrix}{{Y_{F{\lbrack N\rbrack}} = {\sum\limits_{i = 0}^{X - 1}{\sum\limits_{j = 0}^{Y - 1}{{{Luma}_{F{\lbrack N\rbrack}}\lbrack i\rbrack}\lbrack j\rbrack}}}},} & (4)\end{matrix}$where Luma_(F[N])[i][j] indicates a brightness of pixel (i, j) of thecurrent field F[N], X indicates the row number of the current field F[N]and Y indicates the column number of the current field F[N].

When the field brightness difference Diff_Luma corresponding to thecurrent field F[N] is greater than a previous field brightnessdifference and a field brightness threshold Diff_Luma_Th, the scenedetector 630 determines that the scene change occurs. The previous fieldbrightness difference is obtained by selecting the maximum fieldbrightness difference from the previous fields F[N−2], F[N−3], F[N−4]and F[N−5]. Namely, the scene detector 630 determines that the scenechange occurs as the following equation (5) is found.Diff_Luma>max(Diff_Lum_(—)2, 3, 4, 5) and Diff_Luma>Diff_Luma_Th,   (5)where Diff_Lum_2, Diff_Lum_3, Diff_Lum_3 and Diff_Lum_5 indicate fieldbrightness differences respectively of the previous fields F[N−2],F[N−3], F[N−4] and F[N−5], and Diff_Luma_Th indicates the fieldbrightness threshold.

In other embodiments, the previous field brightness difference can beobtained by selecting the maximum field brightness difference from theprevious fields F[N−2], F[N−3], F[N−4] and F[N−5] and performing aweighting operation. Namely, the scene detector 630 determines that thescene change occurs as the following equation (6) is found.Diff_Luma>max(Diff_Luma_(—)2, 3, 4, 5)×gain and Diff_Luma>Diff_Luma_Th  (6)

The determinator 660 is connected to the film mode detector 610 and thescene detector 630. When the video datastream is of the film mode andthe scene change occurs, the video datastream possibly containing a poorediting is determined. Namely, when the current field F[N] is at thefilm mode state 8 or 10 and the scene detector 630 determines at theprevious state 7 or 9 that a scene change occurs, the current field F[N]possibly containing a poor editing can be determined. In this case, themultiplexer 670 selects the de-interlacing device 640 as the output tothereby produce the frame for the current field, but the state stillremains at the film mode.

When the current field F[N] is at the film mode state 6, 7 or 9 and thesawtooth detector 620 determines at the previous state 10, 6 or 8 that asawtooth is present to the next field F[N+1], the current field F[N] isdetermined to have a poor editing and the multiplexer 670 selects thede-interlacing device 640 as the output to thereby produce the frame forthe current field F[N] and return to the state 0 (out of the film mode).

For the other conditions different from the cited above, the multiplexer670 selects the direct coupler 650 as the output.

FIG. 9 is a state transition diagram of a system operation in accordancewith the invention. As shown in FIG. 9, for one of the film mode states6 to 10, a poor editing can be detected due to a scene change orsawtooth effect and further processed to thereby obtain a preferredimage quality.

The prior art uses the sawtooth detector to determine whether a poorediting occurs or not, which can predict a poor editing of the nextfield F[N+1] and accordingly avoid the sawtooth occurrence when thecurrent field F[N] and the next field F[N+1] are combined. However, whenthe next two fields F[N+1] and F[N+2] are combined, a frame buffer and aline buffer are required in combination with the sawtooth detector fordetecting the poor editing, which increases the hardware cost.Otherwise, the sawtooth effect still occurs. By contrast, the inventionuses the sawtooth detector 620 in combination with the scene detector630 to thereby predict a poor editing. When the sawtooth effect isdetected by the detector 620 and the film mode is at state 6, 7 or 9, itimmediately goes out of the film mode. When a scene change is detectedby the scene detector 630 and the film mode is at state 8 or 10, themultiplexer 670 selects the de-interlacing device 640 as the output tothereby produce the frame for the current field F[N] but still remain atthe film mode. Thus, the different conditions for a poor editingoccurrence are properly responded but no sawtooth effect occurs.

In view of foregoing, it is known that the invention combines thesawtooth detector 620 and the scene detector 630 to thereby avoid thevideo datastream from producing the sawtooth effect caused by a poorediting in directly coupling two adjacent fields. In addition, the usenumber of frame buffers and line buffers are reduced to further reducethe hardware cost. Thus, the different conditions for a poor editingpresentation are detected and processed to thereby obtain a preferredimage quality.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

1. A video editing detection system, which receives plural fields of avideo datastream for detecting a video editing in the video datastream,the system comprising: a film mode detector, which receives a previousfield F[N−1] and a next field F[N+1] respectively of the videodatastream to accordingly determine whether the video datastream is afilm mode or not; a sawtooth detector, which receives a current fieldF[N] and the next field F[N+1] respectively of the video datastream tothereby determine whether a sawtooth is present to the next field F[N+1]based on a field energy of the current field F[N] and a frame energy ofthe current field F[N] and next field F[N+1]; and a scene detector,which receives the current field F[N], the next field F[N+1] and theprevious field F[N−1] in order to calculate a field brightnessdifference between the current field F[N] and the previous and nextfields F[N−1] and F[N+1], and accordingly determines whether a scenechange occurs; wherein, when the video datastream is the film mode andthe scene change occurs, the video datastream is determined to have thevideo editing.
 2. The system as claimed in claim 1, wherein the filmmode detector is based on a film detection state transition diagram todetermine that the video datastream is of the film mode or a video mode,states 0 to 5 of the film detection state transition diagram are videomode states 0 to 5, and states 6 to 10 of the film detection statetransition diagram are film mode states 6 to 10; and wherein the filmmode detector sequentially produces film mode states 6 to 10 when thevideo datastream is of the film mode, and further determines the currentfield F[N] as the video editing when the current field F[N] is at thefilm mode state 8 or 10 and the scene detector determines at a previousfilm mode state 7 or 9 that the scene change occurs, for the previousfilm mode state 7 corresponds to the film mode state 8 and the previousfilm mode state 9 corresponds to the film mode state
 10. 3. The systemas claimed in claim 2, wherein the current field F[N] is furtherdetermined as the video editing when the current field F[N] is at thefilm mode state 6, 7 or 9 and the sawtooth detector determines at aprevious film mode state 10, 6 or 8 that the sawtooth is present to thenext field F[N+1], for the previous film mode state 10 corresponds tothe film mode state 6, the previous film mode state 7 corresponds to thefilm mode state 6 and the previous film mode state 9 corresponds to thefilm mode state
 10. 4. The system as claimed in claim 3, wherein thecurrent field F[N] has the field brightness difference expressed bymax(|Y_(F[N−1])−Y_(F[N])|, |Y_(F[N+1])−Y_(F[N])|), where Y_(F[N−)1]indicates a brightness average of the previous field F[N−1], Y_(F[N])indicates a brightness average of the current field F[N] and Y_(F[N−1)]indicates a brightness average of the next field F[N+1].
 5. The systemas claimed in claim 4, wherein the brightness average of the currentfield F[N] is expressed by:${Y_{F{\lbrack N\rbrack}} = {\sum\limits_{i = 0}^{X - 1}{\sum\limits_{j = 0}^{Y - 1}{{{Luma}_{F{\lbrack N\rbrack}}\lbrack i\rbrack}\lbrack j\rbrack}}}},$where Luma_(F[N])[i][j] indicates a brightness of pixel (i, j) of thecurrent field F[N], X indicates the row number of the current field F[N]and Y indicates the column number of the current field F[N].
 6. Thesystem as claimed in claim 5, wherein the field brightness differencecorresponding to the current field F[N] is greater than a previous fieldbrightness difference and a field brightness threshold, the scenedetector determines that the scene change occurs.
 7. The system asclaimed in claim 6, wherein the previous field brightness difference isobtained by selecting a maximum field brightness difference fromprevious fields F[N−2], F[N−3], F[N−4 ] and F[N−5].
 8. The system asclaimed in claim 6, wherein the previous field brightness difference isobtained by selecting a maximum field brightness difference fromprevious fields F[N−2], F[N−3], F[N−4] and F[N−5] and performing aweighting operation.
 9. The system as claimed in claim 3, wherein thesawtooth detector determines that the sawtooth is present to the nextfield F[N+1] when the frame energy is greater than the number of pixelsof the field energy of the current field F[N] and exceeds a threshold.10. The system as claimed in claim 9, wherein the field energy of apixel is expressed by:|Luma_(F[N])[i][j]−Luma_(F[N])[i+1][j]|, where Luma_(F[N])[i][j]indicates a brightness of a pixel (i, j) of the current field F[N] andLuma_(F[N])[i+1][j] indicates a brightness of a pixel (i+1, j) of thecurrent field F[N].
 11. The system as claimed in claim 10, wherein theframe energy of the pixel is expressed by:|Luma_(F[N])[i][j]−Luma_(F[N+1])[i][j]|, where Luma_(F[N])[i][j]indicates a brightness of the pixel (i, j) of the current field F[N] andLuma_(F[N+1])[i][j] indicates a brightness of the pixel (i, j) of thenext field F[N+1].
 12. The system as claimed in claim 3, furthercomprising a de-interlacing device, which receives the current fieldF[N], the previous field F[N−1] and the next field F[N+1] andaccordingly is driven to produce the frame for the current field F[N]when the video datastream is determined to have the video editing. 13.The system as claimed in claim 1, further comprising a direct coupler,which receives the current field F[N], the previous field F[N−1] and thenext field F[N+1] and combines the previous filed field F[N−1] and thenext field F[N−1] or the next field F[N+1] and the current field F[N] tothereby produce the frame for the current field [N] when the videodatastream is determined to have no video editing.